The Nuclear Regulatory Commission (NRC) said it is sending an Augmented Inspection Team (AIT) to the two-unit, 2,200 MW San Onofre Nuclear Generating Station to review the circumstances that led to three tubes failing a pressure test at Unit 3 on March 14.
Operators of the plant shutdown Unit 3 on Jan. 31 after a tube leak in one steam generator was identified. The unit has remained shut down and NRC has had a steam generator expert and additional inspectors at the site inspecting the licensee’s activities and tests of the steam generator tubes.
On Wednesday, March 14, the NRC said three tubes in Unit 3 failed a pressure test indicating they would be more likely to rupture during certain plant events that affect the pressure inside the steam generator. The test involves pumping water inside a tube and increasing the pressure while monitoring a pressure gauge to evaluate the integrity of the tube. Regulators said the integrity of steam generator tubes is important because the tubes provide an additional barrier inside the containment building to prevent a radioactive steam release. Steam generators do experience some wear during the first year of operation but the level of tube wear at Unit 3 is unusual.
The AIT has assumed responsibility from the resident inspectors for gathering information about the current condition and will travel to the site. The team will review information associated with the design, construction, shipping, operation, and testing of the Unit 3 steam generators. The team’s report will not contain inspection findings, but will identify areas for further inspection follow-up.
Subscribe to Nuclear Power International magazine